The present invention is directed to the field of electronic printing of labels and, more particularly, to the field of electronic printing of linerless pressure sensitive labels.
In the area of on-demand label printing, there is a desire to reduce label cost and label waste. To achieve these goals, linerless label stock has been developed. Linerless label stock is especially attractive for use with direct thermal printers. Such linerless direct thermal label stock forms a self-contained imaging system, needing only the controlled application of heat to form an image.
Linerless label stock has been previously described in published literature. Essentially, linerless label stock or recording paper is comprised of a face sheet with a release layer coated over a first side. The face sheet is comprised of a paper carrier or other substrate with a print receptive layer coated on its first side. In the case of direct thermal linerless label stock, the print receptive layer is an image formation layer containing chemical reactants that combine to form a colored image upon controlled application of heat energy. For direct thermal linerless label stock or recording paper, the release layer is preferrably electron beam or UV cured silicone. A pressure sensitive adhesive is coated on a second side of the face sheet. The linerless label stock may be delivered to the user in roll form with the label stock self-wound around a cylindrical core. The roll of linerless label stock may be loaded into a printer by the user. In use, the roll is unwound from the label supply of the printer and passed through a printing station. The release layer provides ease of separation from the pressure sensitive adhesive layer during this process.
Of special concern is the passage of the linerless label stock through the printer with a minimized risk of jamming. The prior art describes several attempts to facilitate this process.
One embodiment, an aspect of the present invention teaches methods and apparatus for providing a linerless label stock or recording paper which, when used in the manner proscribed, exhibits reduced tendency to jam the linerless label printer.
In another aspect, the present invention teaches a linerless label stock having a self-contained imaging layer not prone to heat degradation. Such a media allows the application of linerless label stock technology to a much broader array of use applications than the prior art and also eliminates the necessity of disposing of spent printing supplies.
In another aspect, the present invention teaches a linerless label stock having an adhesive deadening agent printed at intervals over the pressure sensitive adhesive to form regions that are substantially non-tacky. The use of adhesive deadening agent to reduce tack has the advantage of allowing high volume production of linerless label stock converter rolls that do not need to be custom coated with adhesive. Deadening agent is applied in a desired pattern and at a desired repeat distance on a label press at low cost and late in the label production process rather than on a much higher volume adhesive coating machine.
In another aspect, the present invention teaches a linerless label stock that has a pattern coated adhesive formed on its back side. Perforations are formed in the web at locations indexed to the areas with no adhesive. The perforations have the advantage of easing separation of printed labels from the remainder of the web.
In another aspect, the present invention teaches a linerless label stock or recording paper compatible with self-contained printing technologies. The use of a self-contained printing technology with a linerless label stock results in having no spent supplies to dispose of and hence no on-going disposal issues.
In another aspect, the present invention teaches a linerless printer with reduced cost. Cost savings are achieved through the elimination of expensive means to singulate labels after printing such as cutters or specially coated components.
In another aspect, the present invention teaches an apparatus for precisely locating a label perforation relative to the contacting surfaces of a linerless direct thermal label printer.
In another aspect, the present invention teaches a method of operating a linerless printer in a way that reduces the dwell time for contact between exposed adhesive and printer components. Reduction of dwell time limits the tendency for the adhesive""s initial tack to be converted into a permanent bond.
In another aspect, the present invention teaches an improved label tear bar with reduced tendency to stick to the back of pressure sensitive label stock.